I tried to calculate it based on the dimensions, but I got 3 different scales, it might not be totally accurate scalewise...

for the length i got about 1/122, and near 1/82-3ish for the height and width... not sure if its my calculations, or the model thats off though... Probably he was going for about 1/100 ish scale when it was built...

EDIT: LOL SCE you posted while I was typing... but came to the same scales, so that makes me feel better